Brother HL-3450CN - Manual (Page 160)

CHAPTER 6 OPTIONS
6-4
9. Insert the connection cable into
the printer’s connector.
Fig. 6-7
10. Lock the printer and the Tray unit
at the front by turning the Metal
Plate Lock as shown below.
Fig. 6-8
11. Install the covers on both sides
of the Lower Tray Unit. Install the
covers by fitting them first to the
rear of the printer and then fit the
cover into the front of the printer.
Fig. 6-9